1. Field of the Invention
The present invention relates to a device and a method for entering a character string. In particular, the present invention relates to a device and a method for entering a character string, in which there are a plurality of character strings that are output candidates with respect to the input.
2. Description of the Prior Art
The usual method for entering a character string into a computer system is to input characters with a keyboard. However, in the case of languages with an abundance of characters such as Japanese, it is physically impossible to implement a number of keys corresponding to all different characters. Instead, a “kana” character string or a Latin character string (written in “romaji”) is typed into the keyboard, and the character string is entered by kana-kanji conversion.
In order to reduce the number of characters that have to be typed, methods have been proposed, in which characters can be entered using an input prediction function, allowing them to be entered without typing in the entire character string. In addition, methods have been proposed for entering characters without using a keyboard. With such methods, characters can be input by using techniques for character recognition of handwritten characters or voice recognition, for example. Moreover, methods have been proposed for entering characters using only the numeric keys of portable terminals, like portable telephones.
With these methods for entering characters, it is not possible to determine a character string unequivocally from the input, so that, by reference to a suitable dictionary, the appropriate character string is determined from a plurality of character strings that are output candidates.
For example, Publication of Unexamined Japanese Patent Application (Tokkai) No. Sho 61-32186 discloses a method using dictionaries for individual pattern recognition and dictionaries for context processing that are customized for each user. By using a specialized dictionary for each user, the precision of the character string recognition can be enhanced.
Tokkai Hei 9-179859 discloses a method wherein several conversion modes are prepared beforehand, and the candidate character string is determined by selecting a conversion mode that is suitable with respect to the situation when the character string processing device is used.
Moreover, Tokkai Hei 11-3331 discloses a method wherein the field of the text is specified on the basis of the character strings that are being entered in the text, and candidate character strings are determined using a dictionary corresponding to this field.
Thus, the candidate character string corresponding to an input is determined by reference to a dictionary, and can vary slightly depending on the content of the dictionary. For example, if only the input of a specified field is allowed, it is possible to produce a dictionary whose content matches the input of the user.
However, if the input is unspecified, and the content of the dictionary does not match the user's input, there is the problem that the selection efficiency for candidate character strings does not increase, and the hit ratio for input character strings does not increase. For example, even when a dictionary has been prepared beforehand, it cannot accommodate abbreviations that the user has newly created, new product names or other proper nouns, etc.
Also, dictionaries that can be filled so as to sufficiently accommodate unspecified input are conceivable, but that will increase the size of the dictionary, and consume valuable computer resources, so that there is the problem that handwritten character recognition of online pen input in small terminals, such as PDAs (personal digital assistants), cannot be accommodated physically.
For example, the method disclosed in Tokkai Sho 61-32186 attempts to raise context sensitivity by providing customized dictionaries serving as context-sensitive dictionaries, for each user, but it has the drawback that it cannot adapt flexibly to changes in a usage situation.
The method disclosed in Tokkai Hei 9-179859 attempts to raise the hit ratio for candidate character strings by selecting a conversion mode for a situation to determine a candidate character string. However, it is only possible to select from conversion modes that have been prepared beforehand, this method cannot adapt to unpredictable situation. Also, the selection of the conversion mode is left to the user, and there is no guarantee that the user will select the appropriate conversion mode.
Moreover, it is conceivable to store many conversion modes in order to adapt to many situations, but this will consume a lot of valuable computer resources, so that this is physically impossible in small terminals.
Moreover, in the method disclosed in Tokkai Hei 11-3331, the field of the currently edited text is specified, and a dictionary for the specified field is selected, but here the fields themselves have to be specified beforehand, and in a situation such as entering a character string to produce a short message with, for example, a portable telephone, it is generally difficult to specify such fields. Also, to specify such fields, field-specific dictionaries with sufficient capacity are necessary, which will consume a lot of valuable computer resources, so that this is physically impossible in small terminals.